INDIA’S 1ST HIGH RESOLUTION LANDSLIDE SUSCEPTIBILITY MAP

1. In January 2024, IIT Delhi created India’s first high-resolution landslide susceptibility map.
2. In late 2023, heavy floods and landslides triggered by northeast monsoon rains, led to fatalities, emphasizing the need for a national landslide susceptibility map.

What is Landslide Susceptibility Mapping?

1. Landslide Susceptibility Mapping is the process of generating maps illustrating regions susceptible to landslides by considering various factors.
2. Utilizing data on historical landslide and factors such as slope steepness, soil composition, and vegetation cover, a computer model can analyze these elements to forecast areas with a high risk of landslides.

National Landslide Susceptibility Map

1. High-Resolution Mapping: The map offers high resolution, detailing susceptibility at 100m resolution.

1. Identified regions with high susceptibility include parts of the Himalayan foothills, Assam-Meghalaya, and the Western Ghats.

2. Machine Learning Analysis: Utilized a machine learning technique called ensemble learning for improved accuracy and resilience by merging predictions from multiple models.

1. Ensemble Machine Learning involves using multiple machine learning models together to average out the impact of any single model.

3. Factors Considered: The team gathered data on various factors like soil cover, tree density, proximity to roads or mountains.

1. The use of GeoSadak, an online system that has data on the national road network in India, aided in obtaining crucial road network data for remote areas.

4. Significance: Its importance lies in supporting policymakers, conducting vulnerability assessments, and developing mitigation strategies.
5. Future initiatives involve implementing a 'Landslide Early Warning System' utilizing the map data, benefiting organizations such as Geological Survey of India (GSI) and disaster management authorities.

Landslides in India

1. Definition of Landslide: A landslide is the movement of a mass of rock, earth, or debris down a slope.
2. Landslide Prone Regions: Regions with fewer trees, closer to road-building activity, and steeper local slopes are more unstable and prone to landslides.

3. Causes of Landslides in India

1. Natural Causes:

   1. Landslides can occur on various terrains due to conditions such as soil type, rock structure, geological factors, drainage, and slope.
   2. Natural causes include rainfall, undercutting of slopes from flooding or excavation, earthquakes, and snowmelt.

2. Anthropogenic Causes:

1. Human activities like overgrazing, terrain cutting, filling, and excessive development contribute to landslides.
2. For instance, land use changes, deforestation, and slope exposure due to a railway project in western Manipur contributed to a deadly landslide in 2022.

4. Types of Flows

1. Debris Flow: A rapid mass movement involving loose soil, rock, organic matter, and slurry downslope. Commonly caused by intense precipitation or rapid snowmelt.
2. Earth Flow: A downslope viscous flow of fine-grained material saturated with water.
3. Mudflow: A wet or viscous fluid mass of fine and coarse-grained material flowing rapidly along drainage channels.
4. Creep: Slow, steady, downward movement of material under gravity occurring in a large area.

5. Overview of Landslides in India

1. Over the past 50 years, landslides have increased in magnitude and frequency, attributed to human activities.
2. Infrastructure development, like the national initiative Bharatmala Pariyojana, has contributed to the rise in landslides.

6. ISRO’s Landslide Atlas of India Findings:

   1. Global Standing: India is among the top five landslide-prone countries globally, with at least one death per 100 sq km reported annually.
   2. Rainfall Variability Pattern: Primary cause of landslides, with the Himalayas and the Western Ghats being highly vulnerable.
   3. Land Area Prone to Landslide: Excluding snow-covered areas, approximately 12.6% of the country’s geographical land area is prone to landslides.
   4. Regional Variability: 66.5% of landslides are reported from the North-western Himalayas, 18.8% from the North-eastern Himalayas, and 14.7% from the Western Ghats.
   5. Landslides in the Himalayas: The Himalayas witness the most frequent landslide incidents due to their relatively young age and weak, fragile rock structure.

7. Impacts of Landslides:

1. Economic Impacts:
   1. Landslides cause extensive damage to houses, roads, buildings, forests, plantations, and agricultural fields.
   2. Himachal Pradesh estimated a cost of damage from flood and landslides at over Rs 3738 crore due to torrential rains in 2023.
2. Social Impacts: Casualties are more likely in areas with population pressure settled in landslide-vulnerable regions. In 2022, heavy rain, floods, and landslides claimed 835 lives in India.
3. Environmental Impact:
   1. Landslides lead to habitat destruction, soil erosion, and water pollution, altering ecosystems and harming biodiversity.
   2. Soil displacement contributes to increased erosion, negatively impacting water quality and aquatic life.

Case Study: Joshimath Sinking Joshimath, situated on the Rishikesh-Badrinath National Highway (NH-7) in Uttarakhand's Chamoli district, is a hilly town. The town is constructed on old landslide deposits, making its slopes susceptible to destabilization from minor triggers. It falls in Zone V, indicating the highest seismic risk in India's seismic zonation scheme. The area is burdened with structures ignoring the land’s load-bearing capacity. Due to land subsidence, Joshimath developed cracks. Reasons for Joshimath Sinking: Ancient Landslide Site: Joshimath is on a deposit of sand and stone, not on the main rock, as per the 1976 Mishra Committee report. Undercutting by Rivers: River currents of Alaknanda and Dhauliganga contribute to landslides. Inadequate drainage systems aggravate the problem. Geographical Factors: Scattered rocks covered with old landslide debris have low bearing capacity and high pore pressure, especially during monsoons. Construction Impact: Increased construction, hydroelectric projects, and NH widening made slopes highly unstable. The 6-km Helang-Marwari bypass, part of the 825-km Char Dham highway expansion project by the Border Roads Organisation (BRO), faces scrutiny for weakening slopes and destabilizing the local topography. The National Thermal Power Corporation’s Tapovan Vishnugad hydropower project worsens the crisis, according to locals. Land Erosion: Running streams and sliding along natural streams contribute to city fate.

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